This study will investigate the developmental course of attention and conduct problems. Findings will add to our understanding of the overlap between Attention Deficit Hyperactivity Disorder and Conduct Disorders and can be used to identify children with attention and conduct problems who may be most in need of clinical interventions. The purpose of the proposed study is to test the respective roles of attention and conduct problems as risk factors for poor adjustment in later childhood, adolescence, and young adulthood. The 6-year course of attention and conduct problems will be investigated in a nationally representative U.S. general population sample of 2,479 boys and girls ages 4 to 16. Outcomes will be compared for children initially classified in one of the following four groups: (1) Attention Problems without deviance on Delinquent or Aggressive Behavior; (2) Delinquent and/or Aggressive Behavior without Attention Problems; (3) Attention Problems with Delinquent and/or Aggressive Behavior; and (4) control children who were not deviant in attention or conduct problems but who are matched to groups 1-3 for age, sex, ethnicity, SES, and total problem scores. The study will test whether poor outcomes associated with attention problems are accounted for by attention problems per se, the continuation of early comorbid conduct problems, the interaction of initial attention and conduct problems, or overall level of initial behavioral/emotional problems. It will compare the predictive power of additional factors hypothesized to raise or lower the risk of poor outcomes among children who initially show l) attention problems, 2) conduct problems, or 3) a combination of both. It will test whether outcomes are worse for children with attention problems and aggressive behavior than for those with attention problems and nonaggressive delinquent behavior. Sex and age differences in the predictive patterns associated with deviance in attention and conduct problems will be assessed. Findings will be tested for replication across different sources of data within the U.S. national sample (i.e., parent, youth, teacher). Findings from the U.S. national sample will also be tested for replication in a general population sample of Dutch children and in a Vermont sample of clinically referred children who were deviant on the same attention and conduct problem scales as used for the U.S. national sample.